Stress control in baskets

ABSTRACT

A rotary regenerative heat exchanger having a rotor designed to isolate high interior temperature from relatively low exterior temperature in order that thermal difference and distortion resulting therefrom will be maintained at a minimum to enhance the operational efficiency of the heat exchanger.

United States Patent [1 1 Gibson STRESS CONTROL IN BASKETS [75] Inventor: David .1. Gibson, Wellsville, N.Y.

[73] Assignee: The Air Preheater Company, Inc., Wellsville, N.Y.

[22] Filed: June 24, 1974 [21] Appl. No.: 482,538

[52] US. Cl 165/8; 165/10 [51] Int. Cl. F28d 19/00 [58] Field of Search 165/8, 9, 1O

[56] References Cited UNITED STATES PATENTS 2,692,761 10/1954 Waitbus 165/10 X [4 1 Oct. 28, 1975 3,7lO,S51 l/l973 Finnemore 165/10 X FOREIGN PATENTS OR APPLICATIONS 458,882 8/1949 Canada l65/8 Primary Examiner-Albert W. Davis, Jr. Attorney, Agent, or FirmWayne H. Lang [57} ABSTRACT A rotary regenerative heat exchanger having a rotor designed to isolate high interior temperature from relatively low exterior temperature in order that thermal difference and distortion resulting therefrom will be maintained at a minimum to enhance the operational efficiency of the heat exchanger.

3 Claims, 3 Drawing Figures US. Patent Oct. 28, 1975 BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates to rotary regenerative heat exchange apparatus in which a mass of heat absorbent material commonly comprised of packed element plates is positioned in a passageway for a hot gas stream to absorb heat from the hot gases passing therethrough. After the plates become heated by the hot gas they are moved into a cool air passageway where the heated plates transmit their heat to cooler air passing therethrough. The heat absorbent element is carried in open-ended baskets of a rotatable rotor that is surrounded by fixed housing structure including sector plates at spaced ends thereof that separate the hot gas from the cooler air. To prevent mingling of the gas and air, the end edges of the rotor are provided with sealing means that extend outward toward the surrounding rotor housing to bridge the space therebetween and re siliently accommodate a limited amount of thermal expansion and contraction that accompanies normal thermal variations of the rotor. However, excessive thermal variation effects excessive contraction and expansion of the rotor so that each time that it rotates about its axis the rotor is subjected to an extreme amount of thermal distortion and fluid leakage which results therefrom causes a greatly lowered efficiency.

SUMMARY OF THE INVENTION In accordance with my invention I propose to minimize the affects of cool air leakage by providing a nonstructural thermal shield around the rotor shell enclosing a rotor of a rotary regenerative heat exchangerv The thermal shield will isolate the high temperature of the rotor from the cool by-pass air in the plenum chamber between the rotor shell and the rotor housing to result in higher and more uniform temperatures within the rotor, less warping and twisting of the rotor structure, and lower compressive loads on the element carried by the rotor baskets.

BRIEF DESCRIPTION OF THE DRAWING With reference to the drawing:

FIG. 1 is a cross-sectional view of a rotary regenerative heat exchanger having a rotor thereof modified according to this invention,

FIG. 2 is a perspective view ofa single rotor segment, and

FIG. 3 is a cross-sectional view of the rotor shell as seen from 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The arrangement of the drawing shows a rotary regenerative heat exchanger having a central rotor post 12 that is supported at opposite ends on bearings 14 and rotated about its axis by drive means such as a drive motor that is connected through suitable reduction gearing to the rotor post so that it may be rotated slowly about its axis. A mass of heat absorbent material 18 contained in the independent sector-shaped compartments or baskets of the rotor is adapted to absorb heat from hot fluid passing therethrough as as the rotor is rotated about its axis, give it up to a cooler fluid.

The baskets 22 are formed from radial partitions 25 that extend outward from a central rotor post 12 and are welded at their outer ends to arcuate walls 27 that combine with walls of adjacent baskets to form a circular rotorshell. The baskets 22 are open at opposite ends thereof to permit the axial flow of fluid therethrough and they are secured at their radially inner ends to the central rotor post 12.

The rotor is surrounded by a rotor housing 28 having end plates 32 and 34 that include openings 36 and 38 for the inlet and outlet of a heating fluid and similar spaced openings for the inlet and outlet of a fluid to be heated.

To preclude leakage of fluid through the space between the rotor and the rotor housing, sealing means are provided along the end edges of the rotor to bridge the space between the rotor and its surrounding housing. Accordingly, the arcuate ends of the rotor are provided with circumferential seals 46 that are bolted to the end edges of the rotor, and radial seals 48 are secured to the radial walls of the baskets and adapted to rub against the surrounding housing structure as the rotor is rotated about its axis within the housing.

The baskets 22 are joined together at their outer edges by welding or joining together flanges 52 by means such as bolts 54 to form an annular rotor shell that extends concentrically about the rotor post.

Inasmuch as the seals 46 and 48 retard but do not entirely preclude the leakage of fluid into the annular space between the rotor shell and the rotor housing, high pressure air at a cool temperature is continuously leaking into the annular space 56 of the apparatus. However, the heating fluid is flowing continuously through the rotor to subject it to the temperature of the hot fluid. Consequently there is substantial heat flow radially from the hot rotor, through the rotor shell to the cooler leakage fluid in the annular space 56. Movement of heat from the rotor shell outward to the coller air in the annular space 56 predicates a temperature at the rotor shell significantly lower than that centrally within the rotor, a temperature difference that effects a differential of expansion, thermal distortion and ultimate failure of the welds between the radial walls of the rotor and the arcuate walls that comprise the rotor shell.

To preclude heat flowing from the heating element radially outward to the annular space 56 between the rotor shell 28 and the rotor housing 27 and then being transmitted to the leakage fluid flowing therethrough. I provide a heat shield 58 on the outer surface of the rotor shell. This heat shield effectively deters substantially all flow of heat by conduction, convection or radiation whereby the rotor shell 27 is maintained at a high temperature substantially the same as that within the interior of each basket. Inasmuch as the rotor shell and other rotor parts including the rotor diaphragms 25 and the rotor element 18 are comprised of essentially the same material and since they are maintained at a constant temperature, they expand at substantially the same rate to preclude a differential of expansion that might damage the integrity of the weldments therebetween.

The heat shield 58 comprises an outer wall enclosing a space 62 that effectively interrupts the heat flow from the hot rotor element I8 to the cooler space 56. The space may be filled with insulative material 64 of a cellular nature for example, and the inner walls thereof may be coated with reflective material that curtails heat flow by radiation. Inasmuch as all heat flow by conduction. convention and radiation is curtailed. this arrangement maintains the rotor including the rotor shell 27 at a uniform temperature.

I claim:

I. Rotary regenerative heat exchange apparatus in cluding a central rotor post and a cylindrical rotor shell spaced therefrom to provide an annular space therebctween. a mass of heat absorbent element carried in the annular space of the rotor. a housing surrounding the rotor shell in spaced relation to provide a clearance space therebetween, said housing having inlet and outlet ports at opposite ends thereof that direct a heating fluid and a fluid to be heated through the heat absorbent material of the rotor. bearing means supporting the rotor for rotation about its axis within the housing. means for rotating the rotor about its axis a heat shield on the rotor shell adapted to thermally isolate the rotor shell from the clearance space comprising a layer of thermal insulation that precludes the transfer of heat away from the rotor to thus permit the rotor shell to 0perate at substantially the same temperature as the heat absorbent element carried by the rotor.

2. Rotary regenerative heat exchange apparatus having a rotor as defined in claim 1 wherein the thermal insulation includes reflective means that precludes the radiation of thermal energy from the rotor t0 the clearance space.

3. Rotary regenerative heat exchange apparatus having a rotor as defined in claim 2 wherein the heat shield includes an expandible housing that conforms to the thermal expansion of the adjacent rotor shell. 

1. Rotary regenerative heat exchange apparatus including a central rotor post and a cylindrical rotor shell spaced therefrom to provide an annular space therebetween, a mass of heat absorbent element carried in the annular space of the rotor, a housing surrounding the rotor shell in spaced relation to provide a clearance space therebetween, said housing having inlet and outlet ports at opposite ends thereof that direct a heating fluid and a fluid to be heated through the heat absorbent material of the rotor, bearing means supporting the rotor for rotation about its axis witHin the housing, means for rotating the rotor about its axis, a heat shield on the rotor shell adapted to thermally isolate the rotor shell from the clearance space comprising a layer of thermal insulation that precludes the transfer of heat away from the rotor to thus permit the rotor shell to operate at substantially the same temperature as the heat absorbent element carried by the rotor.
 2. Rotary regenerative heat exchange apparatus having a rotor as defined in claim 1 wherein the thermal insulation includes reflective means that precludes the radiation of thermal energy from the rotor to the clearance space.
 3. Rotary regenerative heat exchange apparatus having a rotor as defined in claim 2 wherein the heat shield includes an expandible housing that conforms to the thermal expansion of the adjacent rotor shell. 